DoF questions

Started 2 months ago | Questions thread
ForumParentFirstPreviousNextNext unread
Flat view
AHM
AHM
Regular MemberPosts: 351Gear list
Like?
DoF questions
2 months ago

There are many DoF calculators online, but they don't really answer the following question. Suppose I want to capture a given frame. For example, I want to capture a person 2m tall. I can do that with a 35/f1.8 lens, but I can also move closer with a 20/f1.8 lens (I calculated the required distances as 2.5m and 1.42m; it can be verified here: http://www.bobatkins.com/photography/technical/field_of_view.html). Input into DoF calculators, and the result is exactly the same. Thus DoF (for a given subject) depends ONLY on aperture, not on focal length. Is this correct?

Now I did an experiment. Captured the same subject at 210mm and 50mm both with f/6.3. The results are quite different. The background at 210mm is much more blurry. This seems to contradict the above, but then, not really. Maybe the advantage (or disadvantage) of using a longer focal length is not different DoF, but different blur?

 AHM's gear list:AHM's gear list
Sony a6000 Sony E 55-210mm F4.5-6.3 OSS Sony E 16-50mm F3.5-5.6 PZ OSS Sony E 35mm F1.8 OSS Samyang 12mm 1:2.0 NCS CS
ANSWER:
ForumParentFirstPreviousNextNext unread
Flat view
Post (hide subjects)Posted by
ForumParentFirstPreviousNextNext unread
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark post MMy threads
Color scheme? Blue / Yellow